A conventional scanning laser microscope drives a mirror to reflect the laser light using a scanner, and obtains an image by performing raster-scanning with the laser light that irradiates on a sample.
For example, a scanning laser microscope has a memory for storing a table in which drive waveform data, to indicate each position on which the laser light is irradiated, is registered, and performs scanning with the laser light at the speed according to the read cycle to sequentially read the drive waveform data from the memory (e.g. see Patent Document 1).
In such a scanning laser microscope, the line scanning time for the laser light to scan one line is determined according to a product of a number of data in one line of the drive waveform data that is registered in a table of a memory and a read cycle of the drive waveform data. The frame rate of images obtained by the scanning laser microscope is determined according to a product of the line scanning time and a number of raster-scanned lines.
Also in the scanning laser microscope, the read cycle of the drive waveform data is set by the user selecting a dividing ratio of a divider which converts the reference frequency of clock signals to be a reference of the general operation of the scanning laser microscope. As mentioned above, the line scanning time is determined according to a product of the read cycle of the drive waveform data and the number of data in the drive waveform data, and the frame rate is determined according to a product of the line scanning time and the number of lines. Therefore the frame rate changes discontinuously according to a value multiplied by the number of data in the drive waveform data, or a value multiplied by the number of lines when the dividing ratio changes, and resolution to change the frame rate is determined by the resolution of changing the dividing ratio.    [Patent Document 1] Japanese Patent application Laid-Open No. 2003-98468
However, when the user attempts to slightly change the read cycle by changing only one step of the dividing ratio that can be changed, the desired frame rate may not be able to be selected since the frame rate is changed discontinuously. In other words, images cannot be obtained at an arbitrary frame rate.